Benzo-1,2,3,4-tetrazine 1,3-dioxides: Synthesis and NMR study

Benzo-1,2,3,4-tetrazine 1,3-dioxides (BTDOs) represent fairly stable high-nitrogen systems, incorporating two head-to-tail linked azoxy groups. The synthetic pathway to these heterocycles suggested the use of the tert-butyl-NNO-azoxy group as a building block, allowing the first azoxy group to be incorporated into the ring. The second azoxy group was added with the help of the oxodiazonium ion (-N=N=O+) or its synthetic equivalent. This could be generated by two new methods. The first of these involved treatment of N-nitroamines with nitrating agents, and the second treatment of diazonium salts with peracids in the presence of a base. The proposed key stage in the tetrazine 1,3-bis(N-oxide) ring formation is the reaction between the oxodiazonium ion and the distal nitrogen atom of the tert-butyl-NNO-azoxy group, followed by elimination of the tert-butyl canon. The syntheses of bromo-BTDOs 3b-f and nitro-BTDOs 4a-c are described. The BTDOs were characterized by NMR, including N-14 and N-15 experiments. (C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.